Mourners grieve at one of the makeshift memorials for victims of the Sandy Hook Elementary School shooting, Sunday, Dec. 16, 2012, in Newtown, Conn. On Friday, a gunman allegedly killed his mother at their home and then opened fire inside the school, killing 26 people, including 20 children. (AP Photo/Mary Altaffer)

Sandy Hook school shooting

A man opened fire Dec. 14, 2012, inside the Sandy Hook, Connecticut elementary school where his mother worked as a teacher, killing 26 people, including 20 children, as youngsters cowered in their classrooms and trembled helplessly to the sound of gunfire reverberating through the building.